In court on Tuesday the Commonwealth Solicitor-General argued that the federal government has sole power when it comes to marriage. The Abbott government has not sought an injunction to prevent marriages from taking place, giving couples a five-day window to wed before a decision is published as to whether or not to overturn the law.

When contacted on Tuesday a spokesman for Attorney-General George Brandis declined to comment.

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Senator Brandis has repeatedly refused to comment while the matter is before the court but in October called on the ACT government to stop the laws from taking effect until their constitutional validity was determined.

Ivan Hinton and Chris Teoh arriving at the High Court on Tuesday. Photo: Graham Tidy

Australian Marriage Equality director Rodney Croome said that in "all probability we have a five-day window in which same sex couples will marry on Australian soil for the first time".

"All of those Australians that support marriage equality will be overjoyed that finally in this country we will see same-sex couples marrying," he said.

"We will see the love and commitment these couples share … All the nation will see that just because they're marrying the sky won't fall in."

Mr Corbell said that the 47 couples that had already given at least a month's notice of their intention to marry, as required under the law, "clearly demonstrates same-sex couples and their families are yearning to declare their commitment in a marriage ceremony and the ACT law will provide that opportunity". "Everything about this case has been unexpected and I won't be entirely comfortable until we hear the decision," he said. "I am pleased couples will have the opportunity to marry this weekend even with the case pending and the uncertainty.

"Same-sex couples understand these ceremonies aren't without some doubt but I know they will embrace the opportunity to marry under the ACT law this weekend."

Their celebrant, Jody Aulich, said she had nine weddings booked in for Saturday, Sunday and Monday morning.

"I am going to be very busy this weekend," Ms Aulich said.

"This is fabulous news.

"I really didn't think there would be a window of opportunity."

Ms Aulich said she had other couples who had given her notice.

"I wouldn't be at all surprised that if they have given sufficient notice that they start to contact me to get married in this period."

Ivan Hinton will also marry his partner Christ Teoh in the Rose Garden at Old Parliament House on Saturday, followed by a reception at Black Mountain Tower.

Mr Hinton, who is also the deputy director of Australian Marriage Equality, has been married to Mr Teoh under Canadian law for five years.

But the couple have been part of a decade-long fight to marry in front of family and friends at home.

"I'm delighted to say I'm going to be getting married," he said.

"All today [Tuesday] I've been in a state of terror at the idea that my relationship and the relationships of thousands of Australians are potentially going to be decided in this process."

Mr Hinton said couples that married in the five-day window would be fearful their marriages could be invalidated, but that was a risk they understood.

The landmark case before the full High Court bench is expected to decide whether or not the ACT has enacted a law that is in conflict with the federal marriage act and the federal family law act.

The case is the first real test of whether or not states and territories can legislate for same-sex marriage.

Senator Brandis has repeatedly refused to comment in the lead-up to the hearing, but has previously described the ACT's law as a "threat" to the "well-established position" that marriage laws should be nationally uniform.

The Abbott government acted swiftly to strike down the ACT law and mounted its challenge immediately after the Legislative Assembly passed the same-sex marriage bill in October.

The ACT government faced criticism of its bill, which advocates and constitutional law experts claimed had been drafted too quickly and did not go far enough to create a separate status of same-sex marriage to limit the chance it would be overturned by the High Court.

But the ACT government has backed its bill as being constitutionally sound and capable of concurrent operation with federal marriage laws.

Mr Corbell said the government was apprehensive about the hearing but was confident it had "strong arguments to put to the court".